Linkage between earthquakes and crustal magnetization in Taiwan

The active Taiwan orogen is located between the Ryukyu subduction zone in the northeast and the Manila subduction zone in the south. The intensive collision from the northwestward motion of the Luzon Arc has induced enormous earthquakes in and around Taiwan. In this paper, we attempt to relate the occurrence of earthquakes in Taiwan to the crustal magnetization so that we may better understand the possible great earthquake hazard distribution in Taiwan. For that, we have inverted magnetic anomalies to obtain equivalent crustal magnetization distribution in the Taiwan region. In general, high magnetization zones could be considered as relatively rigid zones. The weak zones in between thus would be compressed as a result of lateral plate convergence, causing intensively crustal deformation and earthquakes. The Lukang Magnetization High (LMH), located in mid-west Taiwan, is suggested to dominate the earthquake occurrence in middle Taiwan. Historically large earthquakes and in Taiwan are mostly distributed around the eastern side of the LMH. If we take into account the northwestward convergence of the Luzon Arc or the Philippine Sea Plate, the area in the southeast side of the LMH actually displays more earthquake hazards. The low magnetization zones in mid-central Taiwan have been compressed and escaped sideward; the intensive compression has caused thick crust and crustal earthquakes as deep as 40 km in middle Taiwan. Although both the eastern Central Range and the Luzon Arc show relatively high magnetizations, the Luzon Arc is intrinsically less strong because of its younger and hotter nature. To conclude, undersatnding the distribution of crustal magnetization could help understand the possible zones of great earthquake hazard.